This invention relates generally to dot matrix printer/plotters suitable for producing permanent copy of digitally represented data.
Various devices are well known for producing hard copy printout of digitally represented data. One class of such devices prints fully formed characters, e.g. daisy wheel printers, whereas a different class of devices forms charaters by printing multiple closely spaced dots appropriately arranged within a matrix of dot positions. Although dot matrix impact printers utilizing hammers or wires to strike a paper or ribbon are most widely used, nonimpact dot matrix printers employing other dot print elements, e.g. ink jet, are also well known.
Within the broad class of dot matrix printers, two different categories are readily commercially available; i.e. (1) serial and (2) line. Both categories of dot matrix printers have been widely discussed in the literature; e.g. see Mini-Micro Systems, January 1981, pages 60 and 97.
The dot matrix serial printer is characterized by the use of a print head, typically having nine vertically spaced wires, mounted to move horizontally back and forth across a paper web mounted for vertical movement. As the head moves across the paper, head solenoids are selectively actuated to impact the wires against the paper to print successive dot columns and thus, serially form characters, each typically within a matrix of nine dot positions high and nine dot positions wide. The paper is stepped after each line of characters is printed.
The dot matrix line printer differs from the serial printer in that a row of dots, rather than a line of characters, is printed between successive paper steps. As is described on page 70 of the aforementioned Mini-Micro Systems publication, a typical commercially available dot matrix line printer utilizes a bank of 44 hammers mounted on a shuttle which sweeps each hammer across three character positions over a 0.3 inch movement. As the shuttle sweeps across, the hammers are actuated at each position in the dot row at which a dot is required and the paper is vertically fed one dot row after each full sweep. The process continues through a total of 7 sweeps (or 9 sweeps when descender characters are to be printed) and then the paper is moved by one character line space, and the process is then repeated for the next line of characters.
Several U.S. Patents are directed to various aspects of dot matrix line printers including: Nos. 3,941,051; 4,127,334; 4,236,835.
U.S. patent application No. 259,697, filed May 1, 1981 discloses an improved dot matrix line printer/plotter including multiple print element banks, each mounted to shuttle across the paper path, and operable to concurrently print different dot rows. The multiple banks are coupled to a common shuttle drive motor and arranged so as to sweep in opposite directions to present an essentially balanced load to the motor. In the disclosed embodiment, each bank carries a plurality of hammer assemblies physically supported on a circuit board mounted for linear reciprocal movement. Each such board preferably carries all of the electronic circuitry uniquely associated with the hammer bank supported thereon. Switch means are provided for enabling a user to selectively disable one of said multiple banks to permit the printer to continue to function even if only one of the banks is operable.